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powerpc/smp: Cache CPU to chip lookup
On systems with large CPUs per node, even with the filtered matching of related CPUs, there can be large number of calls to cpu_to_chip_id for the same CPU. For example with 4096 vCPU, 1 node QEMU configuration, with 4 threads per core, system could be see upto 1024 calls to cpu_to_chip_id() for the same CPU. On a given system, cpu_to_chip_id() for a given CPU would always return the same. Hence cache the result in a lookup table for use in subsequent calls. Since all CPUs sharing the same core will belong to the same chip, the lookup_table has an entry for one CPU per core. chip_id_lookup_table is not being freed and would be used on subsequent CPU online post CPU offline. Reported-by: Daniel Henrique Barboza <danielhb413@gmail.com> Suggested-by: Michael Ellerman <mpe@ellerman.id.au> Signed-off-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com> Tested-by: Daniel Henrique Barboza <danielhb413@gmail.com> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://lore.kernel.org/r/20210415120934.232271-4-srikar@linux.vnet.ibm.com
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parent
131c82b6a1
commit
c1e53367da
3 changed files with 35 additions and 6 deletions
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@ -31,6 +31,7 @@ extern u32 *cpu_to_phys_id;
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extern bool coregroup_enabled;
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extern int cpu_to_chip_id(int cpu);
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extern int *chip_id_lookup_table;
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#ifdef CONFIG_SMP
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@ -65,6 +65,8 @@
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#define DBG(fmt...)
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#endif
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int *chip_id_lookup_table;
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#ifdef CONFIG_PPC64
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int __initdata iommu_is_off;
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int __initdata iommu_force_on;
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@ -914,13 +916,22 @@ EXPORT_SYMBOL(of_get_ibm_chip_id);
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int cpu_to_chip_id(int cpu)
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{
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struct device_node *np;
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int ret = -1, idx;
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idx = cpu / threads_per_core;
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if (chip_id_lookup_table && chip_id_lookup_table[idx] != -1)
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return chip_id_lookup_table[idx];
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np = of_get_cpu_node(cpu, NULL);
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if (!np)
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return -1;
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if (np) {
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ret = of_get_ibm_chip_id(np);
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of_node_put(np);
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of_node_put(np);
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return of_get_ibm_chip_id(np);
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if (chip_id_lookup_table)
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chip_id_lookup_table[idx] = ret;
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}
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return ret;
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}
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EXPORT_SYMBOL(cpu_to_chip_id);
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@ -1073,6 +1073,20 @@ void __init smp_prepare_cpus(unsigned int max_cpus)
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cpu_smallcore_mask(boot_cpuid));
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}
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if (cpu_to_chip_id(boot_cpuid) != -1) {
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int idx = num_possible_cpus() / threads_per_core;
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/*
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* All threads of a core will all belong to the same core,
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* chip_id_lookup_table will have one entry per core.
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* Assumption: if boot_cpuid doesn't have a chip-id, then no
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* other CPUs, will also not have chip-id.
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*/
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chip_id_lookup_table = kcalloc(idx, sizeof(int), GFP_KERNEL);
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if (chip_id_lookup_table)
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memset(chip_id_lookup_table, -1, sizeof(int) * idx);
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}
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if (smp_ops && smp_ops->probe)
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smp_ops->probe();
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}
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@ -1468,8 +1482,8 @@ static void add_cpu_to_masks(int cpu)
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{
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struct cpumask *(*submask_fn)(int) = cpu_sibling_mask;
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int first_thread = cpu_first_thread_sibling(cpu);
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int chip_id = cpu_to_chip_id(cpu);
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cpumask_var_t mask;
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int chip_id = -1;
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bool ret;
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int i;
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@ -1492,7 +1506,10 @@ static void add_cpu_to_masks(int cpu)
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if (has_coregroup_support())
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update_coregroup_mask(cpu, &mask);
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if (chip_id == -1 || !ret) {
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if (chip_id_lookup_table && ret)
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chip_id = cpu_to_chip_id(cpu);
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if (chip_id == -1) {
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cpumask_copy(per_cpu(cpu_core_map, cpu), cpu_cpu_mask(cpu));
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goto out;
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}
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